The present invention relates generally to electrical switches suitable for use in high power environments, and more specifically relates to explosively-actuated switches suitable for use in such environments.
Many types of explosively actuated switches have been proposed for various applications. Explosively actuated switches typically perform their switching functions very quickly. Such switches are thus utilized in applications where actuation must be accomplished as rapidly as possible. A particular application of explosive switches is where extremely high currents must be carried by the switch and must yet be switched quickly. For example, explosive switches may be utilized with large inductive energy storage, such as may be utilized to power electromagnetic railguns. In such applications, the switch will be closed to provide high current charging of an inductor over an extended period of time, and then will be opened to commute the current to the load, preferably within a few 10's of microseconds. In such applications, the switches must be capable of carrying, for example, 750 kiloamps (kA) to 1.5 megamps (MA), yet must be capable of opening within a few 10's of microseconds. High power explosive switches also have utility in other applications, such as, for example, actuating laser flashlamps and as circuit interrupts in the electric utility industry.
Exemplary prior art explosive switches suitable for carrying high current loads have utilized solid conductive plates. These prior art switches have utilized explosive charges to sever the conductive plate along defined portions to create gaps and to open the electrical circuit. Such switches, although relatively simple in theory and structure, present several significant disadvantages. These prior art switches require a relatively large amount of explosive to overcome the shear strength of the conductor to create the gap. This relatively large amount of explosive creates a substantially greater explosive force than would be desirable, presenting a greater potential safety hazard. Additionally, because of the force which must be applied to shear the conductive plate, and the volume of material which must be moved, these switches are not as fast as would be desirable, in view of the amount of explosive utilized. Additionally, the switch must be, in essence, replaced after every shot, since the entire conductive plate may only be utilized once. This places a relatively high cost on each switch actuation. Further, the voltage holdoff in these conventional switches is limited to that established by the gap opened by the explosive. However, the conductive borders of these explosively opened gaps will often include ragged edges, which may promote arcing across the gap.
Accordingly, the present invention provides a new method and apparatus for switching high current circuits through an explosively opened switch which may utilize an optimally minimal amount of explosive to open a specific gap, which amount may be adjusted in response to the specific application in question. Further, the switch may, in large part, be reutilized. Additionally, in one preferred embodiment, the switch provides an insulative piston to block the "line of sight" across the opened switch gap to maximize voltage standoff across the gap.